1a. Objectives (from AD-416):
This research will investigate the response of random inbred lines of soybean to elevated ozone concentrations in the field at the SoyFACE experiment. We will use existing tools from high throughput genomics, metabolomics, comparative and quantitative genetics, and bioinformatics to elucidate the mechanisms of soybean yield response to elevated ozone.
1b. Approach (from AD-416):
This project will use physiological and biochemical analysis, comparative and quantitative genetics, and bioinformatics to study the mechanisms of soybean yield response to elevated ozone.
3. Progress Report:
We identified two soybean genotypes, Dwight and Pana, with different yield responses to elevated ozone. Hybrid F1 seed was produced from these cultivars in 2008. Development of this experimental population prior to 2010 involved advancement of lines from the F2 to the F5 generation through single seed descent. The F5 seed was planted in the field under ambient conditions in 2010 in order to generate sufficient F6 RIL seed for the 2011 ozone field experiment. To ensure ozone response will not be confounded by time to maturity, recombinant inbred lines (RILs) that showed transgressive segregation for maturity under ambient field conditions in 2010 were identified and excluded from the 2011 experiment. In 2010, the parent lines were also grown under 9 different ozone concentrations at the SoyFACE facility in Urbana, Illinois in order to characterize their dose-response and to identify the optimal elevated ozone concentration for the 2011-2013 experiments. Photosynthesis, leaf area development, antioxidant capacity, and yield of the parent lines were also assessed. In 2011, we successfully screened the lines under elevated ozone at SoyFACE and monitored plant development, leaf chlorophyll content and leaf photosynthetic capacity. We had a target ozone fumigation of 100 ppb and were within 20% of that target for 88–93% of the time that the fumigation was on in the 8 rings. We used leaf spectral properties to estimate photosynthetic capacity and validated the use of this technique with infrared gas exchange on the parent lines. We also measured yield in the population and found strong evidence for transgressive segregation of ozone tolerance in the population. We have extracted DNA from all of the individuals in the population and performed initial analysis to confirm the lines are Dwight x Pana progeny. We will genotype the RILs using the Universal Soy Linkage Panel, an array of 1,536 SNP loci, generate a genome-wide linkage map and use that to identify QTL for ozone tolerance. In 2012, we planted the RILs at SoyFACE and are midway through the second season of screening. We have also started collaborating with ARS researchers in St. Louis, Missouri to evaluate the ion content on the soybean seed exposed to elevated ozone.